Veterans of NASA's Project Mercury reunited Saturday to celebrate the 50th anniversary of John Glenn's orbital flight, visiting the old launch pad and meeting the famed astronaut himself.

The first American to orbit the Earth thanked the approximately 125 retired Mercury workers, now in their 70s and 80s, who gathered with their spouses at Kennedy Space Center to swap stories and pose for pictures.

John Glenn stands on the 11th deck of the service tower after his orbital attempt on Jan. 27, 1962, was postponed at Cape Canaveral, Fla. He was launched into orbit on Feb. 20. (NASA/Associated Press)

"We might have been the focal point of attention, but you were all the ones making the whole thing possible," Glenn told the crowd.

Glenn and Scott Carpenter, the only other survivor of NASA's original Mercury 7 astronauts, spent nearly an hour being photographed with the retirees, posing in front of a black curtain with a model of a Mercury-Atlas rocket. Glenn is 90; Carpenter is 86.

Earlier in the afternoon, the Mercury brigade travelled by bus to Launch Complex 14, the pad from which Glenn rocketed away on Feb. 20, 1962.

Some retirees were in wheelchairs, while others used walkers or canes. But they all beamed with pride as they took pictures of the abandoned pad and of each other, and went into the blockhouse to reminisce over old Mercury photos.

'Remember, John, this was built by the low bidder.'— Astronaut Scott Carpenter as recalled by retired NASA engineer Norm Beckel Jr.

Retired engineer Norm Beckel Jr. recalled being seated in the blockhouse right beside Carpenter as the astronaut called out to Glenn right before liftoff, "Godspeed, John Glenn." But there's more to the story, Beckel said.

"Before he said that, he said, 'Remember, John, this was built by the low bidder,"' Beckel, 81, told The Associated Press.

The Mercury-Atlas rocket shook the domed bunker-like structure, although no one inside could hear the roar because of the thick walls.

"Nothing was said by anybody until they said, 'He's in orbit,' and then the place erupted," Beckel recalled.

Beckel and Jerry Roberts, 78, a retired engineer who also was in the blockhouse that historic day, said almost all the workers back then were in their 20s and fresh out of college. The managers were in their 30s. "I don't know if I'd trust a 20-year-old today," Beckel said.

"They don't know it, but we would have worked for nothing," Roberts added.

John Glenn is launched into space on Feb. 20, 1962, becoming the first American to orbit the Earth. (NASA/Associated Press)

The Mercury team included women, about 20 of whom gathered for the anniversary festivities.

"We weren't secretaries, we were mathematicians," said Lucy Simon Rakov, 74, a pioneering computer programmer who travelled from Boston for the reunion.

NASA's celebration of Glenn's three-orbit, five-hour flight aboard the Friendship 7 capsule began Friday at Cape Canaveral. The festivities move to Columbus, Ohio, on Monday, the actual anniversary. Glenn will be honoured at a gala at Ohio State University; its school of public affairs bears his name.

His wife of 68 years, Annie, who turned 92 Friday, and their two children are accompanying him to all the festivities.

Glenn served in the U.S. Senate for 24 years, representing his home state of Ohio. He ran unsuccessfully for president in 1984. He returned to space in 1998 aboard shuttle Discovery, becoming the oldest spaceman at age 77.